#include <iostream>
#include <vector>

using namespace std;

class Solution 
{
public:
    int takeAttendance(vector<int>& records) 
    {
        int left = 0, right = records.size() - 1;
        int mid = 0;
        while (left < right)
        {
            mid = left + (right - left) / 2;
            if (records[mid] == mid)
                left = mid + 1;
            else
                right = mid;
        }
        return records[left] == left ? left + 1 : left;
    }
};
int main()
{
    vector<int> records = { 0, 1, 2, 3, 4, 5, 6, 8 };
    
    Solution xz;
    int n = xz.takeAttendance(records);
    cout << n << endl;

	return 0;
}